/Engine/Source/Editor/UnrealEd/Public/MRUList.h
Checks to make sure the file specified still exists. If it does, it is moved to the top of the MRU list and we return true. If not, we remove it from the list and return false.
true if the item exists, false if it doesn't
bool VerifyMRUFile ( int32 ItemIndex, [FString](API\Runtime\Core\Containers\FString) & OutPackageName )